Miniature metal halide lamps have been on the market for some time, where the lamps are designed to be small and provide concentrated sources of light for inclusion into reflectors. The objective is to gather and focus or collimate the light for projection applications or injection into fiber optics for decorative or medical applications. Examples of this are well known in the art: vitreous silica high-intensity discharge (HID) lamps for automotive headlamps that project a beam for driving at night, and short-arc rare gas lamps for fiber illuminators. Recently the vitreous silica headlamps have been augmented with ceramic metal halide lamps of small dimensions for similar purposes as taught by Guenther U.S. Pat. No. 7,045,960; Wijenberg et. al. WO2004/023517 A1; Hendricx et. al. WO2005/088673 A2; and Selezneva et. al. US 2007/0120492 A1. The lamps may or may not contain mercury. An example of a lamp used for medical applications, namely fiber optic illuminators for surgical applications, is the Cermax® lamp, containing only a high pressure Xe gas filling.
Attempts to combine the integral short arc features of the Cermax® lamp with a filling that remains unobtrusive during operation have been less than satisfactory. Lamp operation in saturated regimes where salts are free to condense at cold spots almost guarantees the salts will coat the windows and occlude the light, filter and change the color, likely in a random and unwanted fashion.
There is a need for a more efficacious short-arc lamp in the 10-50 W range that can produce focused light, but that uses the more efficient light generation potential of metal halide fills.